@md-plugins/md-plugin-headers

A Markdown-It plugin that extracts and processes headers from Markdown content. This plugin is ideal for generating Table of Contents (ToC) or managing headers for documentation and static sites.

NOTE: When using with vue-router be sure to use history mode and not hash mode otherwise your hash links will not work as expected.

Features

Extracts headers based on specified levels (e.g., h1, h2, h3).
Supports custom slugification for header IDs.
Allows custom formatting for header titles.
Provides nested structure for headers (e.g., hierarchical ToC generation).
Compatible with Markdown-It environments for additional flexibility.

Installation

Install the plugin via your preferred package manager:

# with pnpm:
pnpm add @md-plugins/md-plugin-headers
# with Yarn:
yarn add @md-plugins/md-plugin-headers
# with npm:
npm install @md-plugins/md-plugin-headers

Usage

Basic Setup

import MarkdownIt from 'markdown-it';
import { headersPlugin } from '@md-plugins/md-plugin-headers';
import type { MarkdownItEnv } from '@md-plugins/shared';

const md = new MarkdownIt();
md.use(headersPlugin, {
  level: [1, 2, 3], // Extract h1, h2, and h3 headers
  slugify: (str) => str.toLowerCase().replace(/\s+/g, '-'),
  format: (title) => title.toUpperCase(),
});

const markdownContent = `
# Header 1

## Subheader 1.1

### Subheader 1.1.1
`;

const env: MarkdownItEnv = {};
const renderedOutput = md.render(markdownContent, env);

console.log('Rendered Output:', renderedOutput);
console.log('Extracted Headers:', env.toc);

Example Output

The plugin processes headers and stores them in the toc property of the Markdown-It environment (env):

[
  {
    "level": 1,
    "title": "HEADER 1",
    "id": "header-1",
    "link": "#header-1",
    "children": [
      {
        "level": 2,
        "title": "SUBHEADER 1.1",
        "id": "subheader-1-1",
        "link": "#subheader-1-1",
        "children": [
          {
            "level": 3,
            "title": "SUBHEADER 1.1.1",
            "id": "subheader-1-1-1",
            "link": "#subheader-1-1-1",
            "children": []
          }
        ]
      }
    ]
  }
]

Options

The md-plugin-headers plugin supports the following options:

Option	Type	Default	Description
level	number[]	[2, 3]	Heading levels to extract (e.g., [2, 3] for h2, h3).
slugify	function	(str) => str	Function to generate slugs for header IDs.
format	function	(str) => str	Function to format header titles.
shouldAllowNested	boolean	false	Whether to allow headers inside nested blocks (e.g., lists, quotes).

Advanced Usage

Generating a Table of Contents (ToC)

With the toc property in env, you can build a ToC dynamically:

function generateToC(toc) {
  const list = toc
    .map((item) => {
      const children = item.children ? `<ul>${generateToC(item.children)}</ul>` : ''
      return `<li><a href="${item.link}">${item.title}</a>${children}</li>`
    })
    .join('')
  return `<ul>${list}</ul>`
}

const tocHtml = generateToC(env.toc)
console.log('Generated ToC:', tocHtml)

Custom Slugify Function

You can use your own slugification logic for header IDs:

md.use(headersPlugin, {
  slugify: (str) => encodeURIComponent(str.replace(/\s+/g, '_')),
})

Whatever you use on the backend, should be the same logic on the frontend for slugification so that they match when using hash links.

Nested Headers

Enable nested headers to include headers inside blockquotes or lists:

md.use(headersPlugin, {
  shouldAllowNested: true,
})

Testing

pnpm test

Documentation

In case this README falls out of date, please refer to the documentation for the latest information.

License

This project is licensed under the MIT License. See the LICENSE file for details.